Process for extracting the pure cellulose from the bagasse of sugar cane



May 24, 1927 1,630,147

E. C. H. VALET PROCESS FOR EXTRACTING THE PURE CELLULOSE FROM THEBAGASSE OF SUGAR CANE Filed Aug. 9. 1925 MM) hf' Patented May 24, 1927.

UNITEDSTATES EABNEST CHARLES HEMMER VALET, OF MEXICO CITY, MEXICO.

PATENT oFF1cE;.-i f.

PROCESS FOR EXTRACTINGTHE PURE CELLULOSE FROM THE BAGASSE OF SUGAR vCANE.

The present invention refers to a process and apparatus for extractingand separating the pure cellulose from the bagasse of sugar cane, inorder to utilize this cellulose in the manufacture of paper, cardboardand similar products.

The invention has for its object to provide a simple and inexpensiveprocess by which the cellulose pulp may be manufactured at the placewhere the sugar cane is grown and crushed, and from where it may be sentin a compressed form to the factories which convert it into paper,cardboard and similar products. The princi a1 difficulty encountered upt this date in t e separation of the pure cellulose from the bagasse ofthe sugar .cane

consisted in obtaining a thorough eliminat1on of the saccharoseremaining in the bagasse after crushing, and of the resinous I and othercomponents of the stalks. A complete elimination of all foreign mattersis accomplished by the process described hereinafter.

The sugar cane, before or after it has passed through the mill, iscut byadequate machinery into lengths of about one inch and carried byconveyors to the macerating tanks wherein takes place the first step ofthe process. The cane mill may also be com nected directly with irontanks ofa suitable construction and provided with an agitatingmechainsm, and the macerating liquid may be heated by exhauststeam.-

The macerating tanks which as already mentioned may be located at acertain distance from the mills or adjacent to the same, are filled witha clear solution of about 3 to 5% of lime, and the bagasse is left toremain in this solution during a variable time which depends from thesystem of tanks used and from the temperature of the solu- Q tion, whichtemperature however should'not In case the bagasse has not been cut upinto small lengths before being subjecteditol the treatment with thelime solution, this may be done now before introducing it intothecooking tanks.

In the accompanying drawing is shown a preferred form of a cooking tankused for carrying out the present process. As will be seen from thisdrawing, a round tank I 1 is provided with twocovers 2 and 3, prefbeinrrunited, they may also be placed sepaassuEa Application filed August 9,1926, Serial N0. 128,305, and in Mexico June 14, 1926.

ratefy one above the other, but the upper cover should fit tightly intothe sidewalls of the tank 1. The cooking apparatus is provided withsuitable piping 7 for admitting either direct or indirect steam.

The cooking tanks are filled as high as.

possible with the bagasse taken out of the macerating tanks, and with aliquid consisting of a solution of about 6% of caustic soda and ofasolution of from 2 to 3% of sodium sulphite, in the proportion of about18 allons of the caustic soda solution and 12 gallons of the sodiumsulphite solution, making 30 gallons of both solutions combined, forevery 100 pounds of drybagasse. I The com-- position of the liquid mayfurther be varied by adding a new solution of 3% of lime,

according to the class of bagasse to be treated, which varies with itsage and the place where it has been grown. In some cases there may alsobe used a weak solution of calcium sulphite, reducing proportionally theamount of sodium sulphite solution. Instead of sodium sulphite, sodiumhypo-sulphite may also be used.

hen the cooking tanks have been filled with the bagasse and with thesolutions already described and determined according to the propertiesand composition of the bagasse, steam is admitted to the tank throughthe pipe 7, and the bagasse is cooked at a pressure of from 7 to 8pounds and during 4 to 6 hours which is sufficient-time for separatingcompletely the pure cellulose from the other components of the bagasse.

The perforated cover 3, through its own 'holes of the lower cover.

weight and the additional weight of the upper cover 2, resses down onthe bagasse during the who e cooking process, in order that the bagassemay not be revolved in the tank by the inrushing steam and by thecirculating solution but will stay quiet without moving. This is anessential part of the process, as otherwise the percentage of purecellulose obtained would be greatly diminished. The solution however iscontinually forced through the mass of the bagasse, being pushed up bythe entering steam throu'gh avertical pipe 8 which rests ona perforatedcone 9 provided at the bottom of the tank and over the steam inlet; fromthere the solution overflows as indicated by arrows into the spacebetween the two covers 2 and 3, and enters the tank again through theAfter passing downward through the bagasse, it is sucked in tfgain bythe incoming steam through the per orated cone 9 and into the pipe 8.This pipe is partly surrounded by a wider tube 10 connected with thelower cover 3, and on top of the steam inlet there is placed a hood 11having a number of openings, which serves to divert the steam laterallyso that it may push before it the solution which enters through the cone9 and raise it through the pipe 8.

After the cooking process is finished, the solution is drawn olf andfresh steam is admitted which washes the cellulose remainin in the tankand cleans it of all the disso ved substances. The pure cellulose isthen taken out and placed in suitable tanks to be bleached withchlorine, chlorides or similar substances, or it may also be bleachedelectrically.

After bleaching the cellulose may be sent to paper making machines ofany system, according to the class of paper, cardboard etc. to be made;the bagasse cellulose pulp may either be used alone or mixed with pulpfrom other materials. I v What I claim is 1. A process for extractingthe pure cellulose from the bagasse of sugar cane, which consists infirst treating the 'bagasse with a solutiozi of 3 to 5% of lime, inboiling it afterwards under ressure in a solution of about 6% of causticsoda combined with a solution of 2 to 3% of sodium salts until all theforeign matter has been dissolved and se arated from the cellulose, incleaning the co lulose thus obtained with fresh steam after having drawnoff the solutions, and in bleaching the pure cellulose.

2. A process for extracting the pure cellulose from the bagasse of sugarcane, as set forth in claim 1, including the step of cutting up thebagasse into small pieces before it undergoes a treatment in boilers.

3. A process for extracting the pure cellulose from the bagasse of sugarcane, which consists in macerating the bagasse in a solution of limecontained in a heated tank provided with agitators, in boiling it underpressure in a solution of caustic soda and a solution of sodium salts,in a proportion of about 18 gallons of caustic soda solution and 12gallons of sodium salts solution to every 100 pounds of dry bagasse, inseparating with a current of fresh steam the dissolved foreign matterfrom the pure cellulose, and in bleaching the pure cellulose withchlorine, chlorides or electrically.

4. A process for extracting the pure cellulose from the bagasse of sugarcane, as set forth in claim 3, including the step of adding to thesolutions of caustic soda and of sodium salts a solution of 3% of limein a proportion of about 12 gallons to every 100 pounds of dry bagasse.

5. A process for extracting the pure cellu lose from the bagasse ofsugar cane, as set forth in claim 3, whereinsto the solutions of causticsoda and of sodium salts during the second step of the process, is addeda weak solution of cacium sulphite, reducing eventually the quantity ofsodium salts employed.

In testimony whereof I aflix my signature.

EARNEST CHARLES HEMMER VALET.

